Process of recovering uranium



April 30, 1957 M. D. KAMEN 21,796,701

PROCESS OF RECOVERING URANIUM Original Filed April 21, 1944 s Sheets-Sheet 2 DISSOLVING URANIUM METAL DEPOSITED ON STAINLESS STEEL COLLECTOR IN (I)HOT SOLUTION HNOa (12%) 0R(2) SOLUTION HCI (273a H20; (0 .575) OR(3) SOLUTION H,so (|a,'{)& H,o,( I070 CONDENSATE AND MAKE up v SOLUTION CONDENSING $155 (/1 HNO.! WATER Ni 0R(2)HC/ & 11,0, VAPOR DRUM-4,8048 MQZ EVAPO RATING CONCENTRATED SOLUTION U0 i-O Fe if C Ni PRECIPITATING NH 0H AND FILTERING F/L TRA TE PREC/P/TATES N/(NHJI U2 0, FE: (0H): Cr(OH); To DISCARD OR SALVAGE TO FURTHE R TREATMENT F1 9. 2.

"IN VEN TOR.

BY (a. I W

a ATTORNEY 2,799,701 PRUQESS 01F RECQVEIRIN G URANIUM Martin D. Kamen, Berkeley, Calif., assignor tothe United States of America as represented by the United States Atomic Energy Commission Original application April 21 1944 Serial No. 53,160. Divided and this application; Mar-ch 9, 1945, Serial No. 581,805

9 Claims. (C1. 23-145 The present invention relates to the processing of uranium and more particularly to improvements in certain steps of the process disclosed in the. copending application of James M. Carter and Martini). Kamen, Serial No. 532,159, filed April 21, 1944 now Patent No. 2,758,006. The present application is a division of my co-pending application, Serial No. 532,160, filed April 21, Reference is also made to the additional copending divisional' applications of the same case, namely, Serial Numbers 581,806 new Patent No..2,77.6,l84 and 555L807, now abandoned, both filed on March 9, 1945.

It is an object of the invention to provide an improved process of reclaiming uranium from a calutron.

Another object of the inventionis to .providexan improved process of recovering the. residue of a uranium compound which has been subjected -to treatment in a calutron from the parts of the calutrondisposed ;in the.

source region thereof uponwhich the residue'isdeposited.

Another object of the invention is to provide an improved process of recovering. metallic uranium from the collector of a calutron uponqwhich the metallic uranium is deposited.

A further object of the invention is to provide an improved process of :purifying uranium which has been recovered from a calutron.

A further object of the invention is to provide a process of reclaiming uranium from a wash solution derived from a calutron in which the uranium is separated from metal impuritiesin the wash. solution by ether extraction.

A further object of the inventionis to provide fl'sPl'OCt'ZSS of reclaiming uranium from awash-solution derived from a calutron inwhich iron asa metal'irnpurit-y is separated from the uranium inthe wash-solution 'byeth'er extraction.

A further object of the invention is to provide-an improved process of salvaging fractions of uranium from solutions which havelbeenpreviously subjected toprimaryuranium recover treatment in which the solution {is subjected to an ether extraction treatment.

The invention, both as to itsorganization :andvmethod of operation, together with further objects and advan- October9, 1944 now 'Patent No. 2,709,222, and is employed to separate the constituentisotopes of an elementand .more particularly to increase the :proportion of "a selected isotope in an elementcontaining-a plurality-of isotopes in order to produce the .elementenr icheti with the selectedisotope. l

mired States, Patent n 2,790,701 Patented Apr. 30, 1957 Such a calutron essentially comprises means for vaporiz: ing a quantity of material containing an element which is to be enriched with a selected one of'its several isotopes; means for subjecting the'vapor to ionization, whereby at least a portion of the vapor is ionized causing ions of the several isotopes of the element to be produced; electrical means for segregating the ions from the tin-ionized vapor and for accelerating the segregated ions to relatively high velocities; electromagnetic means for deflecting the ions along curved paths, the radii of curvature of the paths of ions being proportional to the square roots of the masses of the ions, whereby the ions are concentrated in accordance with'their masses; and means for tie-ionizing and collecting the ions of the selected isotope thus concentrated, thereby to produce a deposit of the element enriched with the selected isotope.

When such a calutron is employed to separate the isotopes of uranium, the tin-ionized portion of said material which is vaporized is deposited in the source region of the calutron and upon stainless steel surfaces while the ionized portion is deposited partially on the collector and partially upon various surfaces of the vacuum tank and other interior surfaces dependent upon the type of ion which is produced by said ionization and upon the operating characteristics of said .caiutron. it has been found convenient to employ uranium tetrachloride as the material being vaporized and, accordingly, there will be a deposit of the residue thereof formed in the source region orsaid calutron while metallic uranium comprising substantially only U will be deposited in one pocket of the collector of said calutron. and metallic uranium enriched with U and U Will be deposited in the second pocket of said collector.

Considering now the details of the recovery of the metallic uranium from 0116 ofthe pockets in the colle'ctor of the calutron, reference is made to the flow diagram illustrated lll'FlgS. 1 and 2. The inner surfaces of said pocket are etched-with one of a number of acid solutions, whereby the deposit of. metallic uranium is dissolved and various impurities including iron, chromium and nickel are introduced in {the acid wash solution, due to the fact that the inner surfaces ofsaid pocket are formed of stainless steel which comprises the materials mentioned. Accordingly, the wash acid contains at least the following ions:*UO-z++, =Fe+++, -Cr+++ and 7Ni++. A

A suitable acid wash solution'which may be employed for the purpose mentioned comprises an aqueous solutw rl-containing-1-1NO31(6% to 40% by weight, and preferably approximately 12%). Another suitable acid wash solution comp-rises an aqueous solution containing HCl (0.5%"to 2.5% by Weight, and preferably approxi mately 2%) and H202 (025% to 2.0% by weight, and preferably approximately 0.5%). A further 'sui-table acid wash solution comprises an aqueous solution containin HasOi to 30% by weight, and preferably approximately 18%;) and H202 (-5 to 15% by weight, and preferably approximately 10%). Thus, it will be understood that the first acid wash solution comprises an oxidizing acid, Whereas the second and 'third acid wash solutions contain a separate oxidizing agent in the form of H20 Hence, the acid-wash solution employed in any case produces an oxidizing effect upon both the uranium and the metal impurities which are dissolved therein. l

Lin the event the wash acid israt'he-r dilute in the ions mentioned, itmay be concentrated by evaporationyotherwise this IQP {is omitted. In the event the wash acid is concentrated ,byevaporationthe vapor which is driven fi' s on c se a d t i i add e ou JliQlWllP I B .01 Hil d H 02; or H 04 and H20 de nd ing upon the composition of the original wash acid employed, in order to provide a new wash acid which is again used to wash the pocket of the collector of the calutron, in the manner previously explained. This step, comprising condensing the vapor which is driven off the wash acid incident to concentration by evaporation, is advantageous, in view of the fact that any uranium entrained in the vapor is not lost to the outside.

The original wash acid mentioned above, or the concentrated wash acid following evaporation, in the event this step is employed, is then subjected to ammonia treatment, either with excess NH; gas or carbonate-free NHiOH, whereby (NH4)2U2O7, Fe(OH)3 and Cr(OH)s are precipitated away from the nickel in the solution in the form of the ammonia complex ion, Ni(NH3)4++. The solution is then filtered and the precipitate, consisting of ammonium diuranate, ferric hydroxide and chromic hydroxide, is then washed with water containing about one percent NH4OH and one percent (NH4)2SO4 in order to eliminate occluded nickel ammonia complex ion.

Similarly, said residue of UCl4 deposited on the parts of a calutron is recovered by the following method. The parts mentioned disposed in the source region thereof are scrubbed and washed with hot Water, whereby the residue of UCl4 deposited thereon is dissolved; and various impurities including copper, iron, chromium, nickel and carbon, are introduced in the water wash, due to the fact that the various parts of the calutron which are thus washed with hot water are formed of the materials mentioned. The wash water is then sieved in order to remove any solid impurities which may be picked up, such, for example, as small pieces of metal and carbon. These solid impurities may be either discarded or subjected to salvage treatment in order to recover any occluded uranium. The sieved wash water is then treated with H202 by adding a slight excess of ten percent H202 and agitating the solution in order to oxidize the various contained materials. For example, the wash water prior to the step of oxidation may contain suspended U(OH)4 and bits of copper and carbon, dissolved uranium in the +4 and +6 valence states, as well as dissolved copper, iron, nickel, chromium and possibly other metals in one or more of the positive valence states. Hence, as a result of the oxidation all of the uranium is put in solution as uranyl ion, suspended copper is put in solution as cupric ion, and other dissolved materials are put in their higher stable valence states, if they are not already in such state.

Accordingly, the oxidized wash water contains at least the following: UO2++, Cu++, Pe Cr+++, Ni++ and (carbon). The oxidized wash water is then filtered in order to remove C which may be discarded or subjected to salvage treatment in order to recover any occluded uranium.

In'the event this filtrate is rather dilute, it may be concentrated by evaporation; otherwise, this step is omitted. In the event the filtrate is concentrated by evaporation, the water vapor which is driven off is condensed and to it is added enough makeup water in order to provide a new wash solution, which is used again to wash the parts of the calutron disposed in the source region thereof, in the manner previously explained. This step, comprising condensing and re-using the water vapor which is driven off the filtrate incident to concentration by evaporation, is advantageous in view of the fact that any uranium entrained in the water vapor is not lost to the outside. I

The original filtrate mentioned above, or the concentrated filtrate following evaporation, in the event this step is employed, is then subjected to ammonia treatment, either with excess NHs gas or carbonate-free NH4OH, whereby (NH4)2U2O7, Fe(OH)s and Cr (OH)3 are precipitated substantially completely away from the copper and nickel which remain in the solution in theform of ammonia complex ions, Cu(NI-I3)4++ and Ni(NH3)4++.

i The solution is then filtered and the precipitate, consisting of ammonium diuranate, ferric hydroxide and chromic hydroxide, is then washed with water containing about one percent NH4OH and one percent (NH4)2S04, in order to eliminate occluded copper and nickel ammonia complex ions.

Considering the details of the subsequent purification of one of the composite precipitates described above, comprising (NH4)2U2O7, Fe(OH)3 and Cr(OH)3, reference is made to the portion of the flow diagram illustrated in Fig. 3, wherein the ether extraction process is indicated. The manner in which the ether extraction process is carried out depends upon the relative amounts by weight of uranium and iron impurity contained in the composite precipitate. The composite precipitate is considered to contain a large amount of iron when the amount of iron is equal to or greater than the amount of uranium contained; and the composite precipitate is considered to contain a small amount of iron when the amount of iron is less than the amount of uranium contained.

More particularly, when the composite precipitate contains alarge amount of iron, it is dissolved in HCl and the acidity of the solution is adjusted to approximately 6N in hydrochloric acid; whereby the aqueous solution contains UOzClz, FeCls and CrCls. To the solution (C2H5)2O is added and the mixture is vigorously agitated, whereby the FeCls is transferred to the ether and dissolved therein. The ether is then separated from the aqueous solution, whereby the ferric chloride is extracted. This ether extraction step is repeated twice, whereby approximately 98% to 99% of the iron is removed. The ether, containing primarily FeCls, is then discarded or subjected to salvage treatment; and the extracted aqueous solution, containing UOzClz, Cl'Cls and a trace of FeCla, is concentrated by evaporation, whereby water vapor is given off. This solution is then treated with concentrated HNOa in the evaporation step, whereby all of the chlorides are converted to nitrates and C12 and NO gases are given off. More particularly, the treated solution comprises UO2(NO3)2, Cr(N03)3 and a trace of Fe(NO3)3, and is next diluted with water to make the nitric acid concentration from 3N to 6N. This aqueous nitrate solution is then ready for subsequent ether extraction.

In the foregoing description of the extraction of FeCls from an aqueous solution, it will be understood that isopropyl ether, (CsH7)zO, may be utilized equally as well as diethyl ether, (CzH5)2O.

On the other hand, when the composite precipitate contains a small amount of iron, it is directly dissolved in HNOa, whereby the solution contains UO2(NO3)2, Cr(NO3)3 and Fe(NO3)3, and is next diluted with water to make the nitric acid concentration from 3N to 6N. This nitrate solution is then ready for subsequent ether extraction.

To either of the prepared aqueous solutions containing uranyl nitrate, chromic nitrate and ferric nitrate there is added (CzH5)2O and the mixture is vigorously agitated, whereby the UOz(NOs)2 is transferred to the ether and dissolved therein. The ether is then separated from the aqueous solution, whereby the uranyl nitrate is extracted. The extracted aqueous solution containing the chromic nitrate and the ferric nitrate is then discarded or subjected to salvage treatment; and the ether containing the uranyl nitrate is evaporated. When the ether containing the dissolved uranyl nitrate is thus evaporated, (CzH5)2O is driven oif, which is discarded or subjected to salvage treatment, leaving solid uranyl nitrate. The solid uranyl nitrate thus obtained is calcined at about 350 C. to produce U03, whereby N02 and O2 gases are given otf incident to the calcin-ation. The uranium thus purified, and in the compound form U03, is then stored for further treatment or commercial use, as previously noted.

In the foregoing .description of the extraction of UOz(NOs)2 from an aqueous solution, it will be understood that isopropyl ether, (Cal-17320, "may be utilized equally as well as. diethyl ether; (C2He)20.

In view of therforegoing, it 'is apparent that there :has been provided an improved process of recovering, reclaiming, salvaging, purifying and converting uranium, both in metallic and compound-forms.

Also, it will be understood that the present process :may be suitably modified so that a compound of. uranium other than UCl4 may be treated". .For example, ithecalutron, as well as the conversion steps of the process, may be modified, whereby UCls, UBr4, etc. may be treated in order to produce uranium.

The term uranium is employed in the present specification and claims in a generic sense, i. e., as applying to uranium whether in elemental, combined or ionic form, unless indicated otherwise by the context.

Throughout the foregoing specification, the percentages, ratios, and other relations concerning the various elements and compounds are given with respect to weights, unless otherwise indicated by the context.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover-in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a process for reclaiming uranium values from calutron parts which contain metals soluble in the wash solution and upon which parts said uranium is deposited, the steps comprising washing said calutron parts with an aqueous solvent for the uranium, whereby impurity iron in an amount at least equivalent to the uranium is introduced into the wash solution, treating the wash solution with ammonia to precipitate the uranium together with the iron impurity, dissolving the precipitate in hydrochloric acid, contacting the acid solution obtained thereby with ether to extract the iron impurity therein and away from the uranium in said solution, separating the hydrochloric acid solution from the extract, and recovering the uranium from said acid solution.

2. In a process for reclaiming uranium values from calutron parts which contain metals soluble in the wash solution and upon which parts said uranium is deposited, the steps comprising washing said calutron parts with an aqueous solvent for the uranium, whereby metal impurities including iron are also introduced into the wash solution, treating said wash solution with ammonia, thereby precipitating uranium, iron and metal impurities insoluble in the ammonia solution, dissolving the uranium and at least an equivalent amount of the iron impurity of the precipitate in hydrochloric acid, contacting the hydrochloric acid solution obtained thereby with ether to extract the iron into the ether and away from the uranium in said solution, separating the hydrochloric acid solution from the extract, and recovering the uranium values from the hydrochloric acid solution.

3. In a process for reclaiming uranium values from calutron parts which contain metals soluble in the wash solution and upon which parts said uranium is deposited, the steps comprising washing the calutron parts with an aqueous solvent for the uranium, whereby uranium and impurities including iron in amounts at least equivalent to the uranium and chromium are introduced into the wash solution, treating the wash solution with ammonia, thereby precipitating uranium and the iron and chromium impurities, dissolving the uranium, iron and chromium from the precipitate with hydrochloric acid, contacting the hydrochloric acid solution with ether to extract the iron away from the uranium and chromium which remain therein, separating the hydrochloric acid solution from the extract, and separating the uranium values from the chromium in the hydrochloric acid solution.

4. In a process for reclaiming uranium values from calutron parts which contain metals soluble in the wash,

solution and upon which parts" said uranium is deposited,

the steps comprising washing the calutron parts with an aqueous solvent for uranium, whereby uranium and metal impurities including iron and nickel are introduced into' the 'wash solution, treating the wash solution with ammonia, thereby precipitating uranium and at least an equivalent amount of iron away from the nickel impurity in said solution, dissolving precipitate in hydrochloric acid, contacting the hydrochloric acid solution with ether to extract iron away from the uranium in said hydrochloric acid solution, separating the hydrochloric acid solution from the extract, and recovering the uranium from said hydrochloric acid solution.

5. In a process for reclaiming uranium values from calutron parts which contain metals soluble in the wash solution and upon which parts said uranium is deposited, the steps comprising washing the calutron parts with an aqueous solvent for the uranium, whereby uranium and metal impurities including iron :are introduced into the wash solution, treating the wash solution with ammonia, thereby precipitating uranium and some :of the metal'irn purities including iron in amounts less than equivalent to the uranium, dissolving the uranium and impurity precipitates in nitric acid, contacting the nitric acid solution with ether to extract the uranium into the ether and away from impurities remaining in the nitric acid solution, separating the extract from the nitric acid solution, and recoveringthe uranium from the extract.

6. In a process for reclaiming uranium values from calutron parts which contain metals soluble in the wash solution and upon which parts said uranium is deposited, the steps comprising washing said calutron parts with an aqueous solvent for uranium, whereby uranium and metal impurities including iron and nickel are introduced into the wash solution, treating said wash solution with ammonia to precipitate uranium and less than equivalent amounts of iron away from the nickel impurity in said wash solution, separating the precipitate from the wash solution, dissolving the precipitate in nitric acid, contacting the nitric acid solution with ether to extract the uranium into the ether and away from the iron impurity remaining in the nitric acid, separating the extract from the nitric acid solution, and recovering the uranium from the extract.

7. In a process for reclaiming uranium values from calutron parts which contain metals soluble in the wash solution and upon which parts said uranium is deposited, the steps comprising washing said calutron parts with an aqueous solvent for the uranium, whereby metal impurities including nickel, iron in amounts at least equivalent to the uranium and chromium are introduced into the wash solution, treating the wash solution with ammonia to precipitate uranium, iron, and chromium away from the nickel impurity in the wash solution, separating the precipitate from the wash solution, dissolving the precipitate in hydrochloric acid, contacting the hydrochloric acid solution with ether to extract the iron into the ether and away from the uranium and chromium in said hydrochloric acid solution, separating the hydrochloric acid solution from the extract, heating the hydrochloric acid solution containing uranium and chromium to evaporate water and volatile chlorides therefrom while adding an excess of nitric acid thereto to convert the uranium and chromium to the nitrate in a nitric acid solution, cooling the nitric acid solution, contacting said nitric acid solution with ether to extract the uranium away from the chromium which remains therein, separating the extract from the nitric acid solution, and recovering the uranium from the ether extract.

8. In a process for reclaiming uranium values from calutron parts which contain metals soluble in the wash solution and upon which parts said uranium is deposited, the steps comprising washing said calutron parts with an aqueous solvent for the uranium, whereby metal impurities including nickel, iron in amounts at least equivalent to the uranium'and chromium are introduced therein, treating the wash solution with ammonia to precipitate uranium, iron and chromium away from the nickel purity in the wash solution, separating the precipitate from the wash solution, dissolving the precipitate in strong hydrochloric acid, adjusting the concentration of said hydrochloric acid solution to about 6 N, contacting said 6 N hydrochloric acid solution with ether to extract the iron therein and away from the uranium and chromium in the acid solution, separating the extract from the acid solution, then heating said hydrochloric acid solution to evaporate water and volatile chlorides therefrom and while adding an excess of strong nitric acid to the residual hydrochloric acid solution to convert the uranium and chromium chlorides therein into nitrates and adjusting the nitric acid concentration of the solution to a value in the range of about 3 to 6 N, then contacting the nitric acid solution with ether to extract the uranium therein and away from the chromium in the acid solution, separating the extract from said nitric acid solution, and recovering theuranium from the extract.

V .9; In aprocessfor reclaiming uranium values from calutron parts which contain metals soluble in the wash solution'and upon which parts said uranium is deposited, the steps comprising washing said parts with an aqueous solvent for the uranium and producing a solution containing the uranium values together With iron impurity in an acid phase selected from the group consisting of hydrochloric and nitric, contacting said solution with an ether phase, whereby, with said hydrochloric acid solution, the iron is preferentially extracted therein and, with said nitric acid solution, the uranium is selectively extracted therein, separating the extract from the solution, whereby the uranium and iron are separated, and recovering the separated uranium from the respective phase.

References Cited in the file of this patent UNITED STATES PATENTS 2,227,833 Hixson et al Jan. 7, 1941 

1. IN A PROCESS FOR RECLAIMING URANIUM VALUES FROM CALUTRON PARTS WHICH CONTAIN METALS SOLUBLE IN THE WASH SOLUTION AND UPON WHICH PARTS SAID URANIUM IS DEPOSITED, THE STEPS COMPRISING WASHING SAID CALUTRON PARTS WITH AN AQUEOUS SOLVENT FOR THE URANIUM, WHEREBY IMPURITY IRON IN AN AMOUNT AT LEAST EQUIVALENT TO THE URANIUM IS INTRODUCTED INTO THE WASH SOLUTION, TREATING THE WASH SOLUTION WITH AMMONIA TO PRECIPITATE THE URANIUM TOGETHER WITH THE IRON IMPURITY, DISSOLVING THE PRECIPITATE IN HYDROCHLORIC ACID, CONTACTING THE ACID SOLUTION OBTAINED THEREBY WITH ETHER TO EXTRACT THE IRON IMPURITY THEREIN AND AWAY FROM THE URANIUM IN SAID SOLUTION SEPARATING THE HYDROCHLORIC ACID SOLUTION FROM THE EXTRACT, ADN RECOVERING THE URANIUM FROM SAID ACID SOLUTION. 